Acoustic wave device with tilted interdigital transducer electrode

ABSTRACT

Acoustic wave device is disclosed. the acoustic wave device can include a piezoelectric layer and an interdigital transducer electrode over the piezoelectric layer. The interdigital transducer electrode has a non-zero tilt angle. The non-zero tilt angle can between 5° to 15°. A thickness of the interdigital transducer electrode is at least 40% of a thickness of the piezoelectric layer, 400 nm, or 0.08λ where λ is the wavelength generated by the acoustic wave device.

CROSS REFERENCE TO PRIORITY APPLICATION

This application claims the benefit of priority of U.S. ProvisionalPatent Application No. 63/266,100, filed Dec. 28, 2021 and titled“ACOUSTIC WAVE DEVICE WITH TILTED INTERDIGITAL TRANSDUCER ELECTRODE,”and U.S. Provisional Patent Application No. 63/266,098, filed Dec. 28,2021 and titled “ACOUSTIC WAVE DEVICE WITH INTERDIGITAL TRANSDUCERELECTRODE HAVING NON-ZERO TILT ANGLE,” the disclosures of which arehereby incorporated by reference in their entirety herein.

BACKGROUND Technical Field

Embodiments of this disclosure relate to acoustic wave devices.

Description of Related Technology

Acoustic wave filters can be implemented in radio frequency electronicsystems. For instance, filters in a radio frequency front end of amobile phone can include acoustic wave filters. An acoustic wave filtercan filter a radio frequency signal. An acoustic wave filter can be aband pass filter. A plurality of acoustic wave filters can be arrangedas a multiplexer. For example, two acoustic wave filters can be arrangedas a duplexer.

An acoustic wave filter can include a plurality of resonators arrangedto filter a radio frequency signal. Example acoustic wave filtersinclude surface acoustic wave (SAW) filters and bulk acoustic wave (BAW)filters. A surface acoustic wave resonator can include an interdigitaltransductor electrode on a piezoelectric substrate. The surface acousticwave resonator can generate a surface acoustic wave on a surface of thepiezoelectric layer on which the interdigital transductor electrode isdisposed.

SUMMARY

In one aspect, an acoustic wave device configured to generate a surfaceacoustic wave having a wavelength λ is disclosed. The acoustic wavedevice can include a piezoelectric layer, a first reflector on thepiezoelectric layer, a second reflector on the piezoelectric layer, andan interdigital transducer electrode over the piezoelectric layer andpositioned between the first reflector and the second reflector. Theinterdigital transducer electrode has a tilt angle. The tilt angle isbetween 5° to 15°. A thickness of the interdigital transducer electrodeis at least 0.08λ.

In one embodiment, the interdigital transducer electrode has a pitchthat is wider than a pitch of the first reflector so as to shiftstopband of the acoustic wave device.

In one embodiment, the interdigital transducer electrode includes analuminum layer. The thickness of the interdigital transducer electrodecan be at least 0.09λ.

In one aspect, an acoustic wave device is disclosed. The acoustic wavedevice can include a lithium tantalate piezoelectric layer, and a singlelayer aluminum interdigital transducer electrode over the piezoelectriclayer. The interdigital transducer electrode has a tilt angle. The tiltangle is between 5° to 15°. A thickness of the interdigital transducerelectrode is at least 400 nm.

In one embodiment, the acoustic wave device further includes a firstreflector and a second reflector that are positioned such that theinterdigital transducer electrode is disposed between the firstreflector and the second reflector. The interdigital transducerelectrode can have a pitch that is wider than a pitch of the firstreflector so as to shift stopband of the acoustic wave device.

In one aspect, an acoustic wave device is disclosed. The acoustic wavedevice can include a piezoelectric layer and an interdigital transducerelectrode over the piezoelectric layer. The interdigital transducerelectrode has a tilt angle. The tilt angle is non-zero. A thickness ofthe interdigital transducer electrode is at least 40% of a thickness ofthe piezoelectric layer.

In one embodiment, the interdigital transducer electrode includes analuminum layer. The interdigital transducer electrode can be a singlealuminum layer. The interdigital transducer electrode can be amultilayer interdigital transducer electrode that includes the aluminumlayer and a titanium layer.

In one embodiment, the thickness of the interdigital transducerelectrode can be at least 45% of the thickness of the piezoelectriclayer.

In one embodiment, the thickness of the interdigital transducerelectrode is at least 400 nm.

In one embodiment, the acoustic wave device is configured to generate asurface acoustic wave having a wavelength λ, the thickness of theinterdigital transducer electrode is at least 0.08λ.

In one embodiment, the tilt angle is between 5° to 15°.

In one embodiment, he acoustic wave device further includes a firstreflector and a second reflector positioned such that the interdigitaltransducer electrode is disposed between the first reflector and thesecond reflector. The interdigital transducer electrode can have a pitchthat is wider than a pitch of the first reflector so as to shiftstopband of the acoustic wave device.

In one embodiment, the piezoelectric layer is a lithium tantalate layer.

In one embodiment, the acoustic wave device further includes a supportsubstrate positioned under the piezoelectric layer. The acoustic wavedevice can further include an intermediate layer between thepiezoelectric layer and the support substrate. The support substrate caninclude silicon and the intermediate layer can include silicon dioxide.

In one aspect, an acoustic wave device is disclosed. The acoustic wavedevice can include a piezoelectric layer and an interdigital transducerelectrode over the piezoelectric layer. The interdigital transducerelectrode has a non-zero tilt angle. The interdigital transducerelectrode is configured to shift a stopband of the acoustic wave deviceand to reduce a slanted stopband.

In one embodiment, a total weight of the interdigital transducerelectrode is selected so as to reduce the slanted stopband of theacoustic wave device.

In one embodiment, the interdigital transducer electrode includes analuminum layer. The interdigital transducer electrode can be a singlealuminum layer. The interdigital transducer electrode can be amultilayer interdigital transducer electrode that includes the aluminumlayer and a titanium layer.

In one embodiment, a thickness of the interdigital transducer electrodeis at least 40% of a thickness of the piezoelectric layer.

In one embodiment, a thickness of the interdigital transducer electrodeis at least 400 nm.

In one embodiment, the acoustic wave device is configured to generate asurface acoustic wave having a wavelength λ, a thickness of theinterdigital transducer electrode is at least 0.08λ. The thickness ofthe interdigital transducer electrode can be at least 0.09λ.

In one embodiment, the tilt angle is between 5° to 15°.

In one embodiment, the acoustic wave device further includes a firstreflector and a second reflector that are positioned such that theinterdigital transducer electrode is disposed between the firstreflector and the second reflector. The interdigital transducerelectrode can have a pitch that is wider than a pitch of the firstreflector so as to shift stopband of the acoustic wave device to ahigher frequency as compared to when the pitch of the interdigitaltransducer electrode is equal to the pitch of the first reflector.

In one embodiment, the piezoelectric layer is a lithium tantalate layer.

In one embodiment, the acoustic wave device further includes a supportsubstrate positioned under the piezoelectric layer. The acoustic wavedevice can further include an intermediate layer between thepiezoelectric layer and the support substrate. The support substrate caninclude silicon and the intermediate layer can include silicon dioxide.

In one aspect, an acoustic wave device is disclosed. The acoustic wavedevice can include a piezoelectric layer, a first reflector on thepiezoelectric layer, a second reflector on the piezoelectric layer, andan interdigital transducer electrode over the piezoelectric layer andpositioned between the first reflector and the second reflector. Theinterdigital transducer electrode has a tilt angle. The tilt angle isbetween 5° to 15°. A pitch of the interdigital transducer electrode isdifferent from a pitch of the first reflector to shift a stopband of theacoustic wave device. A thickness of the interdigital transducerelectrode is configured to reduce a slanted stopband.

In one embodiment, the pitch of the interdigital transducer electrode iswider than the pitch of the first reflector.

In one embodiment, the interdigital transducer electrode includes analuminum layer.

In one embodiment, the acoustic wave device is configured to generate asurface acoustic wave having a wavelength λ, and a thickness of theinterdigital transducer electrode is at least 0.08λ.

In one embodiment, the piezoelectric layer is a lithium tantalate layer.

The present disclosure relates to U.S. patent application Ser. No.______ [Attorney Docket SKYWRKS.1195A2], titled “ACOUSTIC WAVE DEVICEWITH INTERDIGITAL TRANSDUCER ELECTRODE HAVING NON-ZERO TILT ANGLE,”filed on even date herewith filed on even date herewith, the entiredisclosure of which are hereby incorporated by reference herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will now be described, by way ofnon-limiting example, with reference to the accompanying drawings.

FIG. 1 shows a top layout view of a SAW resonator.

FIG. 2 shows a top layout view of another SAW resonator.

FIG. 3 shows a top layout view of another SAW resonator.

FIG. 4 is a graph showing measurement results of admittance of a SAWresonator similar to the SAW resonator illustrated in FIG. 1 , and a SAWresonator similar to the SAW resonator 2 illustrated in FIG. 2 .

FIG. 5 is a graph showing measurement results of admittance of pitchmodulated SAW resonators.

FIG. 6A shows a top layout view of a SAW resonator according to anembodiment.

FIG. 6B is a schematic cross sectional side view of the SAW resonator ofFIG. 6A.

FIG. 7 is a graph showing measurement results of the SAW resonator ofFIGS. 6A and 6B used as a transmitter (Tx) filter.

FIG. 8 is a schematic cross sectional side view of a portion of an IDTelectrode according to an embodiment.

FIGS. 9A to 9C are graphs showing frequency response measurement resultsof SAW resonators that are similar to the SAW resonator 4 illustrated inFIGS. 6A and 6B.

FIG. 10 is a schematic diagram of a ladder filter that includes anacoustic wave resonator according to an embodiment.

FIG. 11 is a schematic diagram of a radio frequency module that includesa surface acoustic wave resonator according to an embodiment.

FIG. 12 is a schematic diagram of a radio frequency module that includesfilters with surface acoustic wave resonators according to anembodiment.

FIG. 13 is a schematic block diagram of a module that includes anantenna switch and duplexers that include a surface acoustic waveresonator according to an embodiment.

FIG. 14A is a schematic block diagram of a module that includes a poweramplifier, a radio frequency switch, and duplexers that include asurface acoustic wave resonator according to an embodiment.

FIG. 14B is a schematic block diagram of a module that includes filters,a radio frequency switch, and a low noise amplifier according to anembodiment.

FIG. 15A is a schematic block diagram of a wireless communication devicethat includes a filter with a surface acoustic wave resonator inaccordance with one or more embodiments.

FIG. 15B is a schematic block diagram of another wireless communicationdevice that includes a filter with a surface acoustic wave resonator inaccordance with one or more embodiments.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following description of certain embodiments presents variousdescriptions of specific embodiments. However, the innovations describedherein can be embodied in a multitude of different ways, for example, asdefined and covered by the claims. In this description, reference ismade to the drawings where like reference numerals can indicateidentical or functionally similar elements. It will be understood thatelements illustrated in the figures are not necessarily drawn to scale.Moreover, it will be understood that certain embodiments can includemore elements than illustrated in a drawing and/or a subset of theelements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

Acoustic wave filters can filter radio frequency (RF) signals in avariety of applications, such as in an RF front end of a mobile phone.An acoustic wave filter can be implemented with surface acoustic wave(SAW) devices. SAW devices include SAW resonators, SAW delay lines,ladder filters, and multi-mode SAW (MMS) filters (e.g., double mode SAW(DMS) filters). A SAW resonator can be configured to generate, forexample, a Rayleigh mode surface acoustic wave or a shear horizontalmode surface acoustic wave. Although embodiments may be discussed withreference to SAW resonators, any suitable principles and advantagesdisclosed herein can be implemented in any suitable SAW devices.

In general, high quality factor (Q), large effective electromechanicalcoupling coefficient (k²), high frequency ability, and spurious freeresponse can be significant aspects for micro resonators to enablelow-loss filters, stable oscillators, and sensitive sensors.

SAW resonators can include a multilayer piezoelectric substrate.Multi-layer piezoelectric substrates can provide good thermaldissipation characteristics and improved temperature coefficient offrequency (TCF) relative to certain single layer piezoelectricsubstrates. For example, certain SAW resonators with a piezoelectriclayer on a high impedance layer, such as silicon, can achieve a bettertemperature coefficient of frequency (TCF) and thermal dissipationcompared to similar devices without the high impedance layer. A betterTCF can contribute to obtaining the large effective electromechanicalcoupling coefficient (k²). Various embodiments of SAW devices disclosedherein can have a multilayer piezoelectric substrate (MPS) structure.

SAW resonators can have a relatively strong transverse mode in and/ornear a pass band. The presence of the relatively strong transverse modescan hinder the accuracy and/or stability of oscillators and sensors, aswell as hurt the performance of acoustic wave filters by creatingrelatively severe passband ripples and possibly limiting the rejection.Therefore, transverse mode suppression can be significant for SAWresonators.

Tilted interdigital transducer (IDT) electrodes can be used to suppressspurious responses (e.g., a transverse mode spurious) in multi-layerpiezoelectric substrate (MPS) SAW resonators. However, the tilted IDTcan create an unwanted noise caused by a transverse bus bar reflectionwhich can be observed as a slanted stopband in a frequency response.This disclosure provides a technical solution to suppressing transversemodes of MPS SAW resonators using a tilted IDT and an increased IDTthickness or mass (e.g., a total weight of the IDT electrode structure).The combination of the tilted IDT and increased IDT thickness or masscan improve frequency response relative to tilt angle alone. Variousembodiments disclosed herein can also utilize pitch modulation to shiftstopband of resonator to outside of a frequency range of interest.

Embodiments of SAW resonators disclosed herein include an interdigitaltransducer (IDT) electrode that has a rotation angle and a tilt angle.The rotation angle refers to a third Euler angle Ψ of Euler angles (φ,θ, Ψ) of the crystal orientation of a carrier or substrate (e.g., apiezoelectric layer). An IDT electrode includes bus bars and fingersextending from the bus bars. A SAW resonator with the rotation angle (Ψ)of 0° and the tilt angle (μ) of 0° has a horizontal reference axis thatis in parallel with a wave propagation direction of the SAW resonator(e.g., a crystal reference). The SAW resonator also has a verticalreference axis that is in parallel with a longitudinal direction of afinger of the IDT electrode when the SAW resonator has a rotation angle(Ψ) of 0° and the tilt angle (μ) of 0°. Therefore, the rotation angle(Ψ) can also refer to an angle of the entire IDT electrode structure(the fingers and the bus bar) relative to the horizontal reference axisof the SAW resonator. The tilt angle (μ) refers to an angle of the busbar relative to the horizontal reference axis of wave propagation in theSAW resonator while the fingers of the IDT electrode are parallel to thevertical reference axis.

In a final product, first and second sides of a chip that includes a SAWresonator with the rotation angle (Ψ) of 0° and the tilt angle (μ) of 0°can extend parallel with a bus bar of the SAW resonator, and third andfourth sides of the chip that extends perpendicular to the first andsecond sides can extend parallel with fingers of the SAW resonator. In afinal product, first and second sides of a chip that includes a SAWresonator with the rotation angle (Ψ) of 0° and the tilt angle (μ) of 0°non-zero can extend non-parallel with a bus bar of the SAW resonator,and third and fourth sides of the chip that extends perpendicular to thefirst and second sides can extend parallel with fingers of the SAWresonator. In a final product, first and second sides of a chip thatincludes a SAW resonator with the rotation angle (Ψ) of x° (x beingnon-zero) and the tilt angle (μ) of −x° can extend parallel with a busbar of the SAW resonator, and third and fourth sides of the chip thatextends perpendicular to the first and second sides can extendnon-parallel with fingers of the SAW resonator.

FIG. 1 shows a top layout view of a SAW resonator 1. The SAW resonator 1includes a piezoelectric layer 10, and an IDT electrode 12 and a pair ofreflectors 14, 16 over the piezoelectric layer 10. The IDT electrode 12of the SAW resonator 1 includes a first bus bar 18, a second bus bar 20,and a finger region 22 between the first bus bar 18 and the second busbar 20.

The finger region 22 includes first fingers 24 that extend from thefirst bus bar 18 and second fingers 26 that extend from the second busbar 20. The finger region 22 includes first dummy fingers 28 that extendfrom the first bus bar 18 and second dummy fingers 30 that extend fromthe second bus bar 20. The first and second dummy fingers 28, 30 areshorter than the first and second fingers 24, 26. The first and seconddummy fingers 28, 30 can function as pseudo-electrodes for preventing ormitigating interference with the propagation of a wave generated by thefirst and second fingers 24, 26. The IDT electrode 12 has a first pitchP1 (an IDT pitch) and the reflectors 14, 16 have a second pitch P2 (areflector pitch).

The first bus bar 18 and the second bus bar 20 extend in parallel alonga horizontal axis x. The first fingers 24 and the second fingers 26extend along a vertical axis y that is perpendicular to the horizontalaxis x. A third Euler angle Ψ of Euler angles (φ, θ, Ψ) of the crystalorientation of piezoelectric layer 10 is set to 0°. Therefore, theillustrated IDT electrode 12 of the SAW resonator 1 has a rotation angler relative of 0° and a tilt angle μ. relative to the horizontal axis xof 0°.

FIG. 2 shows a top layout view of a SAW resonator 2. FIGS. 1 and 2 areillustrated along the same horizontal axis and with parallel verticalaxes. The SAW resonator 2 includes a piezoelectric layer 10, and an IDTelectrode 32 and a pair of reflector structures 34, 36 over thepiezoelectric layer 10. The IDT electrode 32 of the SAW resonator 2includes a first bus bar 38, a second bus bar 40, and a finger region42.

The finger region 42 includes first fingers 44 that extend from thefirst bus bar 38 and second fingers 46 that extend from the second busbar 40. The finger region 42 includes first dummy fingers 48 that extendfrom the first bus bar 38. The finger region 42 also includes seconddummy fingers 50 that extend from the second bus bar 40. The IDTelectrode 32 has a first pitch P1 (an IDT pitch) and the reflectorstructures 34, 36 have a second pitch P2 (a reflector pitch).

The IDT electrode 32 of the SAW resonator 2 is tilted relative to theIDT electrode 12 of the SAW resonator 1. The IDT electrode 32 of the SAWresonator 2 has a tilt angle μ. The illustrated IDT electrode 32 has thetilt angle μ of non-zero. The first fingers 44 and the second fingers 46extend along the vertical axis y. A third Euler angle Ψ of Euler angles(φ, θ, Ψ) of the crystal orientation of piezoelectric layer 10 is set to0°. Therefore, the illustrated IDT electrode 32 of the SAW resonator 2has a rotation angle r of 0° and the tilt angle μ of non-zero. In someembodiments, the tilt angle μ can be about 8°. For example, the tiltangle μ can be between 5° to 15°. The IDT electrode 32 of the SAWresonator 2 is oriented on the piezoelectric layer 10 such that theacoustic propagation direction is along the horizontal axis x.

FIG. 3 shows a top layout view of a SAW resonator 3. FIGS. 1 to 3 areillustrated along the same horizontal axis and with parallel verticalaxes. The SAW resonator 3 includes a piezoelectric layer 10, and an IDTelectrode 32 and a pair of reflector structures 34, 36 over thepiezoelectric layer 10. The IDT electrode 32 of the SAW resonator 3includes a first bus bar 38, a second bus bar 40, and a finger region42. The SAW resonator 3 is generally similar to the SAW resonator 2except that the IDT electrode 32 of the SAW resonator 3 is oriented onthe piezoelectric layer 10 such that the first bus bar 38 and the secondbus bar 40 extend along the horizontal axis x, and the fingers 44, 46extends non-parallel with the vertical axis y. Therefore, theillustrated IDT electrode 32 of the SAW resonator 3 has a rotation angler of non-zero and the tilt angle μ of non-zero. The orientation of theIDT electrode 32 and the pair of reflector structures 34, 36 of the SAWresonator 3 helps reduce an area on the piezoelectric layer 10 neededfor the IDT electrode 32 and the pair of reflector structures 34, 36.The IDT electrode 32 of the SAW resonator 3 is oriented on thepiezoelectric layer 10 such that the acoustic propagation direction isangled by the tilt angle μ relative to the horizontal axis x.

FIG. 4 is a graph showing measurement results of admittance of a SAWresonator similar to the SAW resonator 1 illustrated in FIG. 1 , and aSAW resonator similar to the SAW resonator 2 illustrated in FIG. 2 . Themeasurement results indicate that some spurious responses (e.g., atransverse mode spurious) in the admittance of the SAW resonator 2 issuppressed as compared to the admittance of the SAW resonator 1. Themeasurement results also show a stopband (response 1) of the SAWresonator 1 and the SAW resonator 2 at a frequency that may degrade thefilter characteristics. The measurement results further show that theSAW resonator 2 introduces an unwanted response (response 2). Theresponse 2 observed in the measurement result can be caused by atransverse bus bar reflection which can be observed as a slantedstopband in a frequency response. More specifically, since the first andsecond fingers 44, 46 of the IDT electrode 32 are not perpendicular tothe first and second bus bars 38, 40 respectively, portions of the firstand second bus bars 38, 40 can be in the acoustic wave propagationdirection of the IDT electrode 32. Thus, the transverse bus barreflection may be observed as the response 2 or the slanted stopband.

FIG. 5 is a graph showing measurement results of admittance of a SAWresonator similar to the SAW resonator 1 illustrated in FIG. 1 , and aSAW resonator similar to the SAW resonator 2 illustrated in FIG. 2 . TheSAW resonators used in the measurements in FIG. 5 are different from theSAW resonators used in the measurements in FIG. 4 in that the SAWresonators used in the measurements in FIG. 5 have the second pitch P2(the IDT pitch) greater than the first pitch P1 (the reflector pitch).The measurement results of FIG. 5 indicate that pitch modulation canshift the stopband (response 1). By increasing the second pitch P2relative to the first pitch P1, the response 1 can be shifted to ahigher frequency. Accordingly, FIG. 5 indicates that pitch modulationcan be utilized to improve the frequency response by shifting theresponse 1. However, the unwanted response 2 remains in the frequency ofinterest at around 850 MHz for the pitch modulated SAW resonator 2. Invarious embodiments disclosed herein, the first pitch P1 and the secondpitch P2 can be modulated such that the first pitch P1 is within 10% ofthe second pitch P2.

FIG. 6A shows a top layout view of a SAW resonator 4 according to anembodiment. FIG. 6B is a schematic cross sectional side view of the SAWresonator 4 of FIG. 6A. The SAW resonator 4 can include a supportsubstrate 60, a piezoelectric layer 10 over the support substrate 60, anintermediate layer 62 between the support substrate 60 and thepiezoelectric layer 10, and an IDT electrode 64 and a pair of reflectors66, 68 over the piezoelectric layer 10. The IDT electrode 64 of the SAWresonator 4 can include a first bus bar 70, a second bus bar 72, and afinger region 74 between the first and second bus bars 70,72.

The finger region 74 includes first fingers 76 that extend from thefirst bus bar 70 and second fingers 78 that extend from the second busbar 72. The finger region 74 includes first dummy fingers 80 that extendfrom the first bus bar 70. The finger region 74 also includes seconddummy fingers 82 that extend from the second bus bar 72. The IDTelectrode 64 has a first pitch P1 (an IDT pitch) and the reflectors 66,68 have a second pitch P2 (a reflector pitch). In some embodiments, thefirst pitch P1 and the second pitch P2 can be different. For example,the first pitch P1 and the second pitch P2 can be modulated to shift astop band of the SAW resonator 4. The first pitch P1 of the IDTelectrode can set the wavelength λ, of the SAW resonator 4. The firstpitch P1 is typically equal to the wavelength λ.

The IDT electrode 64 of the SAW resonator 4 is tilted relative to theIDT electrode 12 of the SAW resonator 1. The IDT electrode 64 of the SAWresonator 4 has a tilt angle μ. The illustrated IDT electrode 64 has thetilt angle μ of non-zero. The first fingers 76 and the second fingers 78extend along the vertical axis y. Therefore, the illustrated IDTelectrode 64 of the SAW resonator 4 has a rotation angle r of 0° and thetilt angle μ of non-zero. In some embodiments, the tilt angle μ can beabout 8°. For example, the tilt angle μ can be between 5° to 15°. TheIDT electrode 64 of the SAW resonator 4 is oriented on the piezoelectriclayer 10 such that the acoustic propagation direction is along thehorizontal axis x.

The piezoelectric layer 10 can be a lithium tantalate (LT) layer. Forexample, the piezoelectric layer 10 can be an LT layer having a cutangle of 42° (42° Y-cut X-propagation LT). For example, thepiezoelectric layer 10 can be 42±15° Y-cut LT, 42±10° Y-cut LT, or 42±5°Y-cut LT. Any other suitable piezoelectric material, such as a lithiumniobate (LN) layer, can be used as the piezoelectric layer 10.

The support substrate 60 can be a silicon substrate, a quartz substrate,a sapphire substrate, a polycrystalline spinel substrate, a ceramicsubstrate, or any other suitable carrier substrate. In some embodiments,the intermediate layer 62 can act as an adhesive layer. The intermediatelayer 62 can include any suitable material. The intermediate layer 62can be, for example, an oxide layer (e.g., a silicon dioxide (SiO₂)layer).

The piezoelectric layer 10 has a thickness t1 and the IDT electrode 64has a thickness t2. In some embodiments, the thickness t2 of the IDTelectrode 64 can be more than about 40% of the thickness t1 of thepiezoelectric layer 10. For example, the thickness t2 of the IDTelectrode 64 can be more than 40%, 54%, or 50% of the thickness t1 ofthe piezoelectric layer 10. In some embodiments, the thickness t2 of theIDT electrode 64 can be in a range of 350 nm to 450 nm, 350 nm to 400nm, or 400 nm to 450 nm. In some embodiments, the thickness t2 of theIDT electrode 64 can be in a range from 7% to 10% of the wavelength λ ofthe SAW resonator 4. For example, the thickness t2 of the IDT electrode64 can be between 7.35% to 9.45%, 7.35% to 8.4%, or 8.4% to 9.45% of thewavelength λ of the SAW resonator 4. For example, the thickness t2 ofthe IDT electrode 64 can be at least 8%, 9%, or 10% of the wavelength λof the SAW resonator 4. In some embodiments, the thickness t2 of the IDTelectrode 64 can be about 450 nm while the wavelength λ of the SAWresonator 4 is set to about 5.68 μm.

FIG. 7 is a graph showing measurement results of the SAW resonator 4used as a transmitter (Tx) filter. In the measurements, three differentthicknesses of the IDT electrodes were used. The SAW resonator 4 used inthe measurements includes an LT layer for the piezoelectric layer 10, asilicon layer for the support substrate 60, a silicon dioxide (SiO₂)layer for the intermediate layer 62, and an aluminum layer for the IDTelectrode 64. The wavelength λ of the SAW resonator 4 is set to 4.76 μm.

One measurement was taken setting the thickness t2 of the IDT electrode64 to be 35% of the thickness t1 of the piezoelectric layer 10 (350 nmor 7.35% of the wavelength λ). Another measurement was taken setting thethickness t2 of the IDT electrode 64 to be 40% of the thickness t1 ofthe piezoelectric layer 10 (400 nm or 8.4% of the wavelength λ). Anothermeasurement was taken setting the thickness t2 of the IDT electrode 64to be 45% of the thickness t1 of the piezoelectric layer 10 (450 nm or9.45% of the wavelength λ).

The measurement results indicate that the SAW resonator 4 with thickerIDT electrode 64, when the thickness t2 is 40% and 45% of the thicknesst1 of the piezoelectric layer 10, the response is improved as comparedto the SAW resonator 4 when the thickness t2 is 35% of the thickness t1of the piezoelectric layer 10. Therefore, the SAW resonator 4 with thethickness t2 of more than 40% of the thickness t1 can reduce, minimizeor remove the unwanted response 2 (see FIG. 4 ) that would be present inthe frequency of interest at around 850 MHz. The improvements observedfrom the measurement results can be due to at least, for example, theincreased total weight of the IDT electrode structure by having thethickness t2 more than 40% of the thickness t1.

In various embodiments disclosed herein, a SAW resonator frequencyresponse can be improved using a tilted IDT electrode structure withpitch modulation and an IDT electrode thickness t2 of at least 40% ofthe thickness t1 of the piezoelectric layer 10 (400 nm or 8.4% of thewavelength λ). Any suitable principles and advantages disclosed hereincan be used with an IDT electrode that has both a non-zero rotationangle and a non-zero tilt angle. Though some of the embodimentsdisclosed herein are described using one type of resonator (e.g., amultilayer piezoelectric substrate SAW resonator), any suitableprinciples and advantages disclosed herein can be used with any types ofresonators such as a temperature compensated (TC) SAW resonator.

FIG. 8 is a schematic cross sectional side view of a portion of an IDTelectrode 52′ according to an embodiment. The IDT electrode 52′ has amultilayer IDT electrode structure in which two or more layers of metaldefine the IDT electrode 52′. In the illustrated IDT electrode 52′,there are a first titanium layer 86, a second aluminum layer 88 over thefirst titanium layer 86, a third titanium layer 90 over the secondaluminum layer 88, and a fourth aluminum layer 92 over the thirdtitanium layer 90. The IDT electrode 52′ has a thickness t3.

In some embodiments, the IDT electrode 52 of the SAW resonator 4 can bereplaced with the IDT electrode 52′. When the IDT electrode 52′ is usedwith the SAW resonator 4, the thickness t3 of the IDT electrode 52′ canbe the same as or generally similar to the thickness t2 of the IDTelectrode 52 described above.

In various embodiments disclosed herein, an IDT electrode can includeany other suitable IDT electrode material(s). For example, an IDTelectrode can include one or more of an aluminum (Al) layer, amolybdenum (Mo) layer, a tungsten (W) layer, a titanium (Ti) layer, aplatinum (Pt) layer, a gold (Au) layer, a silver (Ag) layer, a copper(Cu) layer, a Magnesium (Mg) layer, a ruthenium (Ru) layer, or the like.The IDT electrode may include alloys, such as AlMgCu, AlCu, etc. In someembodiments, the IDT electrode can be a multi-layer IDT electrode. As anexample, a multi-layer IDT electrode can include an Al layer over a Molayer or an Al layer over a W layer.

FIGS. 9A to 9C are graphs showing frequency response measurement resultsof SAW resonators that are similar to the SAW resonator 4 illustrated inFIGS. 6A and 6B. Different IDT electrode materials are used in thesemeasurements. In FIG. 9A, an aluminum layer IDT electrode with itsthickness of 350 nm was used. In FIG. 9B, an aluminum layer IDTelectrode with its thickness of 400 nm was used. In FIG. 9C, amultilayer IDT electrode including a molybdenum layer with its thicknessof 150 nm and an aluminum layer with its thickness of 200 nm was used.The measurement results indicate that the slanted stopband (response 2)can be reduced, minimized or removed by using these IDT electrodestructures.

Acoustic wave resonators disclosed herein can be included in a filterarranged to filter a radio frequency signal. One or more acoustic waveresonators including any suitable combination of features disclosedherein be included in a filter arranged to filter a radio frequencysignal in a fifth generation (5G) New Radio (NR) operating band withinFrequency Range 1 (FR1). A filter arranged to filter a radio frequencysignal in a 5G NR operating band can include one or more SAW resonatorsdisclosed herein. FR1 can be from 410 megahertz (MHz) to 7.125 gigahertz(GHz), for example, as specified in a current 5G NR specification. Oneor more acoustic wave resonators in accordance with any suitableprinciples and advantages disclosed herein can be included in a filterarranged to filter a radio frequency signal in a fourth generation (4G)Long Term Evolution (LTE) operating band. One or more acoustic waveresonators in accordance with any suitable principles and advantagesdisclosed herein can be included in a filter having a passband thatincludes a 4G LTE operating band and a 5G NR operating band.

FIG. 10 is a schematic diagram of a ladder filter 100 that includes anacoustic wave resonator according to an embodiment. The ladder filter100 is an example topology that can implement a band pass filter formedfrom acoustic wave resonators. In a band pass filter with a ladderfilter topology, the shunt resonators can have lower resonantfrequencies than the series resonators. The ladder filter 100 can bearranged to filter a radio frequency signal. As illustrated, the ladderfilter 100 includes series acoustic wave resonators R1, R3, R5, and R7and shunt acoustic wave resonators R2, R4, R6, and R8 coupled between afirst input/output port I/O₁ and a second input/output port I/O₂. Anysuitable number of series acoustic wave resonators can be in included ina ladder filter. Any suitable number of shunt acoustic wave resonatorscan be included in a ladder filter. The first input/output port I/O₁ cana transmit port and the second input/output port I/O₂ can be an antennaport. Alternatively, first input/output port I/O₁ can be a receive portand the second input/output port I/O₂can be an antenna port.

FIG. 11 is a schematic diagram of a radio frequency module 175 thatincludes a surface acoustic wave component 176 according to anembodiment. The illustrated radio frequency module 175 includes the SAWcomponent 176 and other circuitry 177. The SAW component 176 can includeone or more SAW resonators with any suitable combination of features ofthe SAW resonators disclosed herein. The SAW component 176 can include aSAW die that includes SAW resonators.

The SAW component 176 shown in FIG. 11 includes a filter 178 andterminals 179A and 179B. The filter 178 includes SAW resonators. One ormore of the SAW resonators can be implemented in accordance with anysuitable principles and advantages of the surface acoustic waveresonator 4 of FIGS. 6A and 6B and/or any surface acoustic waveresonators disclosed herein. The filter 178 can be a TCSAW filterarranged as a band pass filter to filter radio frequency signals withfrequencies below about 3.5 GHz in certain applications. The terminals179A and 178B can serve, for example, as an input contact and an outputcontact. The SAW component 176 and the other circuitry 177 are on acommon packaging substrate 180 in FIG. 11 . The packaging substrate 180can be a laminate substrate. The terminals 179A and 179B can beelectrically connected to contacts 181A and 181B, respectively, on thepackaging substrate 180 by way of electrical connectors 182A and 182B,respectively. The electrical connectors 182A and 182B can be bumps orwire bonds, for example. The other circuitry 177 can include anysuitable additional circuitry. For example, the other circuitry caninclude one or more one or more power amplifiers, one or more radiofrequency switches, one or more additional filters, one or more lownoise amplifiers, the like, or any suitable combination thereof. Theradio frequency module 175 can include one or more packaging structuresto, for example, provide protection and/or facilitate easier handling ofthe radio frequency module 175. Such a packaging structure can includean overmold structure formed over the packaging substrate 180. Theovermold structure can encapsulate some or all of the components of theradio frequency module 175.

FIG. 12 is a schematic diagram of a radio frequency module 184 thatincludes a surface acoustic wave resonator according to an embodiment.As illustrated, the radio frequency module 184 includes duplexers 185Ato 185N that include respective transmit filters 186A1 to 186N1 andrespective receive filters 186A2 to 186N2, a power amplifier 187, aselect switch 188, and an antenna switch 189. In some instances, themodule 184 can include one or more low noise amplifiers configured toreceive a signal from one or more receive filters of the receive filters186A2 to 186N2. The radio frequency module 184 can include a packagethat encloses the illustrated elements. The illustrated elements can bedisposed on a common packaging substrate 180. The packaging substratecan be a laminate substrate, for example.

The duplexers 185A to 185N can each include two acoustic wave filterscoupled to a common node. The two acoustic wave filters can be atransmit filter and a receive filter. As illustrated, the transmitfilter and the receive filter can each be band pass filters arranged tofilter a radio frequency signal. One or more of the transmit filters186A1 to 186N1 can include one or more SAW resonators in accordance withany suitable principles and advantages disclosed herein. Similarly, oneor more of the receive filters 186A2 to 186N2 can include one or moreSAW resonators in accordance with any suitable principles and advantagesdisclosed herein. Although FIG. 12 illustrates duplexers, any suitableprinciples and advantages disclosed herein can be implemented in othermultiplexers (e.g., quadplexers, hexaplexers, octoplexers, etc.) and/orin switch-plexers.

The power amplifier 187 can amplify a radio frequency signal. Theillustrated switch 188 is a multi-throw radio frequency switch. Theswitch 188 can electrically couple an output of the power amplifier 187to a selected transmit filter of the transmit filters 186A1 to 186N1. Insome instances, the switch 188 can electrically connect the output ofthe power amplifier 187 to more than one of the transmit filters 186A1to 186N1. The antenna switch 189 can selectively couple a signal fromone or more of the duplexers 185A to 185N to an antenna port ANT. Theduplexers 185A to 185N can be associated with different frequency bandsand/or different modes of operation (e.g., different power modes,different signaling modes, etc.).

FIG. 13 is a schematic block diagram of a module 190 that includesduplexers 191A to 191N and an antenna switch 192. One or more filters ofthe duplexers 191A to 191N can include any suitable number of surfaceacoustic wave resonators in accordance with any suitable principles andadvantages discussed herein. Any suitable number of duplexers 191A to191N can be implemented. The antenna switch 192 can have a number ofthrows corresponding to the number of duplexers 191A to 191N. Theantenna switch 192 can electrically couple a selected duplexer to anantenna port of the module 190.

FIG. 14A is a schematic block diagram of a module 210 that includes apower amplifier 212, a radio frequency switch 214, and duplexers 191A to191N in accordance with one or more embodiments. The power amplifier 212can amplify a radio frequency signal. The radio frequency switch 214 canbe a multi-throw radio frequency switch. The radio frequency switch 214can electrically couple an output of the power amplifier 212 to aselected transmit filter of the duplexers 191A to 191N. One or morefilters of the duplexers 191A to 191N can include any suitable number ofsurface acoustic wave resonators in accordance with any suitableprinciples and advantages discussed herein. Any suitable number ofduplexers 191A to 191N can be implemented.

FIG. 14B is a schematic block diagram of a module 215 that includesfilters 216A to 216N, a radio frequency switch 217, and a low noiseamplifier 218 according to an embodiment. One or more filters of thefilters 216A to 216N can include any suitable number of acoustic waveresonators in accordance with any suitable principles and advantagesdisclosed herein. Any suitable number of filters 216A to 216N can beimplemented. The illustrated filters 216A to 216N are receive filters.In some embodiments (not illustrated), one or more of the filters 216Ato 216N can be included in a multiplexer that also includes a transmitfilter. The radio frequency switch 217 can be a multi-throw radiofrequency switch. The radio frequency switch 217 can electrically couplean output of a selected filter of filters 216A to 216N to the low noiseamplifier 218. In some embodiments (not illustrated), a plurality of lownoise amplifiers can be implemented. The module 215 can includediversity receive features in certain applications.

FIG. 15A is a schematic diagram of a wireless communication device 220that includes filters 223 in a radio frequency front end 222 accordingto an embodiment. The filters 223 can include one or more SAW resonatorsin accordance with any suitable principles and advantages discussedherein. The wireless communication device 220 can be any suitablewireless communication device. For instance, a wireless communicationdevice 220 can be a mobile phone, such as a smart phone. As illustrated,the wireless communication device 220 includes an antenna 221, an RFfront end 222, a transceiver 224, a processor 225, a memory 226, and auser interface 227. The antenna 221 can transmit/receive RF signalsprovided by the RF front end 222. Such RF signals can include carrieraggregation signals. Although not illustrated, the wirelesscommunication device 220 can include a microphone and a speaker incertain applications.

The RF front end 222 can include one or more power amplifiers, one ormore low noise amplifiers, one or more RF switches, one or more receivefilters, one or more transmit filters, one or more duplex filters, oneor more multiplexers, one or more frequency multiplexing circuits, thelike, or any suitable combination thereof. The RF front end 222 cantransmit and receive RF signals associated with any suitablecommunication standards. The filters 223 can include SAW resonators of aSAW component that includes any suitable combination of featuresdiscussed with reference to any embodiments discussed above.

The transceiver 224 can provide RF signals to the RF front end 222 foramplification and/or other processing. The transceiver 224 can alsoprocess an RF signal provided by a low noise amplifier of the RF frontend 222. The transceiver 224 is in communication with the processor 225.The processor 225 can be a baseband processor. The processor 225 canprovide any suitable base band processing functions for the wirelesscommunication device 220. The memory 226 can be accessed by theprocessor 225. The memory 226 can store any suitable data for thewireless communication device 220. The user interface 227 can be anysuitable user interface, such as a display with touch screencapabilities.

FIG. 15B is a schematic diagram of a wireless communication device 230that includes filters 223 in a radio frequency front end 222 and asecond filter 233 in a diversity receive module 232. The wirelesscommunication device 230 is like the wireless communication device 200of FIG. 15A, except that the wireless communication device 230 alsoincludes diversity receive features. As illustrated in FIG. 15B, thewireless communication device 230 includes a diversity antenna 231, adiversity module 232 configured to process signals received by thediversity antenna 231 and including filters 233, and a transceiver 234in communication with both the radio frequency front end 222 and thediversity receive module 232. The filters 233 can include one or moreSAW resonators that include any suitable combination of featuresdiscussed with reference to any embodiments discussed above.

Although embodiments disclosed herein relate to surface acoustic waveresonators, any suitable principles and advantages disclosed herein canbe applied to other types of acoustic wave resonators and/or acousticwave devices that include an IDT electrode, such as Lamb wave resonatorsand/or boundary wave resonators. For example, any suitable combinationof features of the tilted and rotated IDT electrodes disclosed hereincan be applied to a Lamb wave resonator (for example, a Lamb waveresonator) and/or to a boundary wave device (for example, a boundarywave resonator).

Any of the embodiments described above can be implemented in associationwith mobile devices such as cellular handsets. The principles andadvantages of the embodiments can be used for any systems or apparatus,such as any uplink wireless communication device, that could benefitfrom any of the embodiments described herein. The teachings herein areapplicable to a variety of systems. Although this disclosure includessome example embodiments, the teachings described herein can be appliedto a variety of structures. Any of the principles and advantagesdiscussed herein can be implemented in association with RF circuitsconfigured to process signals in a frequency range from about 30kilohertz (kHz) to 300 GHz, such as in a frequency range from about 410MHz to 8.5 GHz.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products such as packaged radio frequency modules and/orpackaged filter components, uplink wireless communication devices,wireless communication infrastructure, electronic test equipment, etc.Examples of the electronic devices can include, but are not limited to,a mobile phone such as a smart phone, a wearable computing device suchas a smart watch or an ear piece, a telephone, a television, a computermonitor, a computer, a modem, a hand-held computer, a laptop computer, atablet computer, a microwave, a refrigerator, a vehicular electronicssystem such as an automotive electronics system, a stereo system, adigital music player, a radio, a camera such as a digital camera, aportable memory chip, a washer, a dryer, a washer/dryer, a copier, afacsimile machine, a scanner, a multi-functional peripheral device, awrist watch, a clock, etc. Further, the electronic devices can includeunfinished products.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,”“include,” “including” and the like are to be construed in an inclusivesense, as opposed to an exclusive or exhaustive sense; that is to say,in the sense of “including, but not limited to.” The word “coupled”, asgenerally used herein, refers to two or more elements that may be eitherdirectly connected, or connected by way of one or more intermediateelements. Likewise, the word “connected”, as generally used herein,refers to two or more elements that may be either directly connected, orconnected by way of one or more intermediate elements. Additionally, thewords “herein,” “above,” “below,” and words of similar import, when usedin this application, shall refer to this application as a whole and notto any particular portions of this application. All numerical values,such as values for rotation angle and tilt angle, in this applicationand the claims are intended to encompass similar values within error ofavailable measurement techniques. Where the context permits, words inthe above Detailed Description using the singular or plural number mayalso include the plural or singular number respectively. The word “or”in reference to a list of two or more items, that word covers all of thefollowing interpretations of the word: any of the items in the list, allof the items in the list, and any combination of the items in the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or withoutauthor input or prompting, whether these features, elements and/orstates are included or are to be performed in any particular embodiment.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel apparatus, methods, andsystems described herein may be embodied in a variety of other forms;furthermore, various omissions, substitutions and changes in the form ofthe methods and systems described herein may be made without departingfrom the spirit of the disclosure. For example, while blocks arepresented in a given arrangement, alternative embodiments may performsimilar functionalities with different components and/or circuittopologies, and some blocks may be deleted, moved, added, subdivided,combined, and/or modified. Each of these blocks may be implemented in avariety of different ways. Any suitable combination of the elements andacts of the various embodiments described above can be combined toprovide further embodiments. The accompanying claims and theirequivalents are intended to cover such forms or modifications as wouldfall within the scope and spirit of the disclosure.

What is claimed is:
 1. An acoustic wave device configured to generate asurface acoustic wave having a wavelength λ, the acoustic wave devicecomprising: a piezoelectric layer; a first reflector on thepiezoelectric layer; a second reflector on the piezoelectric layer; andan interdigital transducer electrode over the piezoelectric layer andpositioned between the first reflector and the second reflector, theinterdigital transducer electrode having a tilt angle, the tilt anglebeing between 5° to 15°, a thickness of the interdigital transducerelectrode being at least 0.08λ.
 2. The acoustic wave device of claim 1wherein the interdigital transducer electrode has a pitch that is widerthan a pitch of the first reflector so as to shift stopband of theacoustic wave device.
 3. The acoustic wave device of claim 1 wherein theinterdigital transducer electrode includes an aluminum layer.
 4. Theacoustic wave device of claim 3 wherein the thickness of theinterdigital transducer electrode is at least 0.09λ.
 5. An acoustic wavedevice comprising: a lithium tantalate piezoelectric layer; and a singlelayer aluminum interdigital transducer electrode over the piezoelectriclayer, the interdigital transducer electrode having a tilt angle, thetilt angle being between 5° to 15°, a thickness of the interdigitaltransducer electrode being at least 400 nm.
 6. The acoustic wave deviceof claim 5 further comprising a first reflector and a second reflectorpositioned such that the interdigital transducer electrode is disposedbetween the first reflector and the second reflector.
 7. The acousticwave device of claim 6 wherein the interdigital transducer electrode hasa pitch that is wider than a pitch of the first reflector so as to shiftstopband of the acoustic wave device.
 8. An acoustic wave devicecomprising: a piezoelectric layer; and an interdigital transducerelectrode over the piezoelectric layer, the interdigital transducerelectrode having a tilt angle, the tilt angle being non-zero, athickness of the interdigital transducer electrode being at least 40% ofa thickness of the piezoelectric layer.
 9. The acoustic wave device ofclaim 8 wherein the interdigital transducer electrode includes analuminum layer.
 10. The acoustic wave device of claim 9 wherein theinterdigital transducer electrode is a single aluminum layer.
 11. Theacoustic wave device of claim 9 wherein the interdigital transducerelectrode is a multilayer interdigital transducer electrode thatincludes the aluminum layer and a titanium layer.
 12. The acoustic wavedevice of claim 8 wherein the thickness of the interdigital transducerelectrode is at least 45% of the thickness of the piezoelectric layer.13. The acoustic wave device of claim 8 wherein the thickness of theinterdigital transducer electrode is at least 400 nm.
 14. The acousticwave device of claim 8 wherein the acoustic wave device is configured togenerate a surface acoustic wave having a wavelength λ, the thickness ofthe interdigital transducer electrode is at least 0.08λ.
 15. Theacoustic wave device of claim 8 wherein the tilt angle is between 5° to15°.
 16. The acoustic wave device of claim 8 further comprising a firstreflector and a second reflector positioned such that the interdigitaltransducer electrode is disposed between the first reflector and thesecond reflector.
 17. The acoustic wave device of claim 16 wherein theinterdigital transducer electrode has a pitch that is wider than a pitchof the first reflector so as to shift stopband of the acoustic wavedevice.
 18. The acoustic wave device of claim 8 wherein thepiezoelectric layer is a lithium tantalate layer.
 19. The acoustic wavedevice of claim 8 further comprising a support substrate positionedunder the piezoelectric layer.
 20. The acoustic wave device of claim 19further comprising an intermediate layer between the piezoelectric layerand the support substrate, the support substrate includes silicon andthe intermediate layer includes silicon dioxide.